I have generally had no problem getting off from blow jobs, but I sometimes find it hard to cum from a handjob (I can always 'get there' quicker on my own). I think it's a matter of communication. Tell your partner what feels good and what doesn't. With hand jobs I find that a pulling, milking action is not right as it doesn't simulate the feel of pushing cock into pussy. Similarly, a lot of suction is not what works (for me) in a blow job. I like to feel a little resistance as my cock goes in. I've never given a blow job so I can't say how easy or difficult it is to produce the right effect, but again I do think it's all about communication.
The other aspect is about how we train ourselves to 'come'. Most of us (men and women) masturbate quite vigorously and at a rhythm that's much faster than you can thrust during sex, and faster than anyone can move their head back and forth when giving a bj. We condition ourselves to come to that pressure and rhythm, so it's not surprising that a bj feels a little alien and some of us have difficulty 'tuning in to the frequency'. But to some extent, that's exactly what you have to do. My wife had never had an orgasm during intercourse, and after watching her masturbate, I wasn't too surprised. She did it with her thighs together and every muscle in her body, it seemed, tense. There was no way she could hold that position while I fucked her, and during sex I could tell she was frustrated by not getting near the sensations that got her off. So I worked hard at helping her to get to the plateau phase whilst relaxed. I distracted her from fixating on the goal of orgasm, and I encouraged her to focus on the sensations she could feel rather than the ones she couldn't feel. Sure enough, in time she learned to relax and melt into the sensations as I humped her slowly with my cock buried to the hilt. Her orgasm hit her like a freight train, and her pussy went wild and triggered mine. That was a very good moment, after which we could pretty reliably have mutual orgasms. I'm sure it must be possible for a couple to similarly train the recipient of the bj to relax and 'get there', but it will take a little time and patience, and a lot of communication.